1. Field of the Invention
This invention relates to a reinforcement binding machine for binding a plurality of reinforcement members that cross each other, that is, longitudinally and laterally oriented reinforcements defining a reinforcement cage, by means of a steel wire.
2. Description of the Prior Art
One type of machine for binding a plurality of reinforcement members that cross each other by means of a steel wire disposed at the intersections of these reinforcements has been disclosed in Japanese Patent Public Disclosure (KOKAI) No. 51265/80. According to this prior art reinforcement binding machine, the steel wire is guided by means of a guide defining a binding station, so as to be wound a number of times around the reinforcements so as to form a loop encircling the reinforcements. Through the loop are inserted a pair of pins from the axially opposed sides of the loop along the axis thereof. The pins are supported by means of a rotor which is rotated about an axis orthogonal to the axis of the pin and extending diametrically with respect to the loop. Thus, the steel wire wound through means of the plurality of turns is twisted by the pins. The respective pins are normally spaced from each other by means of spring force and butted against each other at the time of binding so as to engage the steel wire to be twisted by means of centrifugal force due to the rotation of the rotor exceeding the spring force.
However, the prior art reinforcement binding machine has such a construction that both pins are butted against each other by means of the centrifugal force overcoming the spring force. Therefore, both pins are left spaced from each other even if the rotor is rotated as a result of the centrifugal force not exceeding the spring force as a result of an insufficient rotational speed of the rotor. Under such a condition, the pins are not inserted into the loop so that the steel wire cannot be properly twisted.
Furthermore, in the prior art reinforcement binding machine, when the rotational speed of the rotor is reduced due to the beginning of the twisting of the steel wire, the centrifugal force becomes smaller than the spring force. As a result, even if the pins are inserted into the loop, since the pins are separated from each other by means of the spring force so as to be disengaged from the steel wire, the reinforcements cannot be sufficiently bound. When the rotational speed of the rotor and thus of the pins is increased so as to prevent the defective binding, it is difficult to achieve proper timing and completion of the twisting operation, and consequently, excessive or insufficient twisting is produced since the prior art machine is constructed so as to complete the twisting operation when the centrifugal force becomes smaller than the spring force. In particular, if the steel wire is excessively twisted, it is twisted off or the pins are strongly restrained by means the steel wire even if the steel wire is not twisted off. Therefore, the pins cannot be disengaged from the twisted steel wire by means of the spring force.
Furthermore, in the prior art reinforcement binding machine, since the timing of the butting operation, that is, the closing of the pins against each other and the timing of the disengaging operation, that is, the opening of the pins with respect to each other, depend upon the rotational speed and rotational timing of the rotor, the steel wire cannot be twisted to a predetermined strength.
Also, since the prior art reinforcement binding machine is constructed so as to determine the relative positional relationship between the reinforcements and the reinforcement binding machine according to the experience of an operator, the position of the reinforcements in the binding portion defined by means of the guide for guiding the steel wire in the form of a loop along a curve encircling the reinforcements becomes indefinite. In this case, as the twisting means is rotated at the time of binding, the guide comes into contact with the reinforcements. As a result, the binding operation becomes troublesome.
Furthermore, since the prior art reinforcement binding machine is provided with a cutter for cutting off the steel wire separately from the steel wire twisting means, a cutter driving mechanism and a means for synchronizing the cutter with the steel wire twisting means or the like are needed in addition to the cutter.
Still further, in the prior art reinforcement binding machine, since the twisting means is freely rotatable at the time it is desired to stop its rotation, a steel wire inlet of the twisting means has to be manually aligned with a steel wire outlet of a steel wire feeding path at the time of beginning the binding operation. Furthermore the position of the steel wire inlet of the twisting means has to be manually maintained so as to be aligned with the steel wire outlet of the steel wire feeding path at the time of feeding the steel wire.
Yet further, in the prior art reinforcement binding machine, since a guide path provided within the guide is a groove which opens to the inside of the guide throughout the total length of the guide, the leading end of the steel wire moves along the guide path contacting the depth surface of the guide path as the steel wire is fed while a rear portion escapes from the guide path inwardly of the guide and thus the steel wire cannot be transformed into a loop encircling the reinforcements as a result of the steel wire having a predetermined degree of rigidity.